1. Field of the Invention
The present invention relates to an eyepiece zoom lens system used for telescopes, binoculars, and the like.
2 . Description of the Prior Art
In general, in an eyepiece zoom lens system, a movable space for moving the lens system is necessary, whereby the total length of the lens system tends to become long. Accordingly, it is difficult to configure the zoom lens system in a compact size. Though the power of each lens group may be increased in order to attain a compact size, a larger amount of aberration will be generated thereby. Also, the amount of fluctuation in aberration due to zooming increases, thereby making it difficult to favorably correct the aberration while achieving a high zoom ratio. As examples of an eyepiece zoom lens system, those disclosed in Japanese Unexamined Patent Publication No. 53- 51757 and Japanese Patent Publication No. 7- 34061 have been known.
Though the lens systems disclosed in the above-mentioned publications have favorable performances, each of them has h zoom ratio of 2, which is not always sufficient in terms of the high zoom ratio. In recent years, there has been an attempt to increase the zoom ratio of compact cameras from double power zoom toward triple power zoom, while a demand for increasing the zoom ratio has also become higher in telescopes and binoculars.